1. Field of the Invention
The present invention relates to an ophthalmic photographic apparatus, and more particularly to an ophthalmic photographic apparatus that includes an illumination optical system for projecting illuminating light onto a subject eye fundus via an aperture stop such as a ring slit or the like, and a photographing optical system that photographs the fundus thus illuminated.
2. Description of the Prior Art
There are various ways of photographing the eye fundus in color using an ophthalmic photographic apparatus such as a fundus camera. In mydriatic photography, a mydriatic agent is administered to the eye, which is taxing for the patient. There is also non-mydriatic photography in which a mydriatic agent is not used. In non-mydriatic photography, infrared light is projected onto the fundus and the fundus is photographed after the alignment is completed. There is also fluorescent photography, which includes fluorescein angiography for photographing visible fluorescent images, and ICG (indocyanine green) fluorophotography (ICG angiography) for photographing infrared fluorescent images. Each photography mode uses different illumination and photographing filters, and the optical characteristics also differ. It is, therefore, preferable to use a specialized fundus camera for each mode. However, from the standpoint of cost-performance, fundus cameras are being developed that can be used for various modes. For example, Japanese Laid open Patent Publication No. Hei9-140672 describes a fundus camera that can be used for mydriatic and non-mydriatic photography and fluorescein angiography; Japanese Laid open Patent Publication No. Hei 8-150120 describes a fundus camera that can be used for mydriatic photography (color), fluorescein angiography and ICG fluorophotography; Japanese Laid open Patent Publication No. Hei 1-300926 also describes a fundus camera that can be used for mydriatic photography (color), fluorescein angiography and ICG fluorophotography; and Japanese Patent No. 2894359 describes mechanisms for interlocking variable power lenses, fluorescent filters and ring slits depending upon the photographing modes.
However, for a fundus camera to be able to handle mydriatic, non-mydriatic, fluorescein angiographic and ICG fluorophotographic modes, it has to be able to insert complex combinations of filters into the optical path and retract the filters from the optical path when the system is switched among the four modes. This increases the complexity of the apparatus and of the various setting operations, increasing the misoperations. For these reasons, there is no fundus camera that can handle the above four photographing modes.